Icechecf,
I just went through this. See my post at http://www.chevyavalanchefanclub.com/cafcna/index.php/topic,84766.0.html for the eventual fix.
Based on what I found here, there are three possible problems. First, and easiest to fix is the faulty ground problem. Second is a faulty Elec. Brake Control Module (EBCM). This is what my mechanic diagnosed and wanted to charge me $1000+ to fix for parts and labor to install a new EBCM.
Based on input from this site, I went to modulemaster.com and Gavin there helped me out. Just installed a rebuilt EBCM from him with a 5 year warranty for $190.00 after the $60 credit for returning my used one. Took me less than an hour.
The third possibility is corrosion on the wheel sensor, but that apparently causes the ABS to engage and stay on at low speeds. That occurs mainly in snow belt states where salt and other chemicals cause corrosion of the sensor. If you have just the light problem, it's more than likely one of the other two possibilities.
Try a search for the ground problem and clean the connections. If the lights come back on (mine took a while) it's more than likely the EBCM.
Good luck. Let me know if I can assist further. (But I owe all I know to the others on this site who went before me.)